Radiation therapy apparatus with an aperture assembly and associated methods

ABSTRACT

A radiation therapy apparatus includes a housing, a radiation source carried by the housing, and at least one aperture assembly carried by the housing. The aperture assembly includes a radiation aperture body having a shaped opening therein to control a radiation dosing profile, and an aperture holder with an aperture-receiving passageway therein receiving the radiation aperture body, and having a recessed end. A cover is received within the recessed end of the aperture holder and retains the radiation aperture body within the aperture holder. The cover has an opening aligned with the shaped opening in the radiation aperture body. The radiation aperture body, the aperture receiving passageway of the aperture holder and the opening of the cover have angled interfaces therebetween. A radiation filter is carried by the housing.

RELATED APPLICATIONS

This application is a continuation of prior filed application Ser. No.13/834,772 filed Mar. 15, 2013, which is incorporated herein byreference in its entirety.

FIELD OF THE INVENTION

The present invention relates to the field of radiation therapy, andmore particularly, to an aperture assembly for a radiation therapyapparatus, and related methods.

BACKGROUND OF THE INVENTION

Proton therapy uses a beam of protons to irradiate diseased tissue, mostoften in the treatment of cancer. The chief advantage of proton therapyis the ability to more precisely localize the radiation dosage whencompared with other types of external beam radiotherapy.

During treatment, a particle accelerator is used to target the diseasedtissue with a beam of protons. Due to their relatively large mass,protons have little lateral side scatter in the tissue. The beam doesnot broaden much, stays focused on the shape of the diseased tissue anddelivers low-dose side-effects to surrounding tissue. All protons of agiven energy have a certain range, with very few protons penetratingbeyond this range. The dose delivered to the tissue is maximum just overthe last few millimeters of the particle's range, which is called theBragg peak.

A radiation aperture body (i.e., aperture) and a radiation filter (i.e.,a range compensator) are beam modifying devices that control the shapeand penetration of protons during treatment of a patient. These devicesare typically connected to an output of a radiation source of aradiation therapy apparatus. The radiation aperture body is typicallybrass and can be up to several inches thick, and has a shaped openingtherein to control the radiation dosing profile. The radiation filter isthree-dimensionally shaped to direct the protons to the desired targetarea on the patient to ensure that the target receives the correctradiation dose, while the healthy tissue surrounding the target receivessubstantially less radiation. Careful registration or indexing of theradiation filter and the radiation aperture body ensures that thepatient has the proper exposure in the target area, such that theproton's energy is released within the target area.

A typical radiation therapy apparatus does not fully expose theradiation aperture body to the protons. Consequently, there is a borderregion around the perimeter of the radiation aperture body which is notexposed to the protons. As noted above, the radiation aperture body istypically brass and can be up to several inches thick. Brass is a fairlyexpensive material compared to other high density materials, and theexcess brass in the border region adds to the cost of the radiationaperture body.

One approach to reduce the cost of the radiation aperture body is toreplace a portion of the brass border region with a non-brass frame thatcarries the radiation aperture body, as disclosed in U.S. publishedpatent application no. 2011/0127443. The frame and the radiationaperture body are dimensioned so that the radiation aperture body isstill not fully exposed to the protons, but since the volume of theradiation aperture body is reduced, less brass is needed resulting in acost savings. Nonetheless, there is still a need to further reduce thecost of a radiation aperture body.

SUMMARY OF THE INVENTION

In view of the foregoing background, it is therefore an object of thepresent invention to provide a radiation therapy apparatus with a lowcost radiation aperture body.

This and other objects, features, and advantages in accordance with thepresent invention are provided by a radiation therapy apparatuscomprising a housing, a radiation source carried by the housing, and atleast one aperture assembly carried by the housing. The apertureassembly may comprise a radiation aperture body, an aperture holder anda cover. A radiation filter may also be carried by the housing. Theradiation source may generate protons, for example.

More particularly, the radiation aperture body may have a shaped openingtherein to control a radiation dosing profile. The aperture holder mayhave an aperture-receiving passageway therein receiving the radiationaperture body, and a recessed end. The cover may be received within therecessed end of the aperture holder, and retains the radiation aperturebody within the aperture holder. The cover may have an opening alignedwith the shaped opening in the radiation aperture body.

The aperture holder and cover may advantageously be formed out of adifferent material from the radiation aperture body. For example, theradiation aperture body may be formed out of brass, whereas the apertureholder and cover may each be formed out of stainless steel or other highdensity material other than brass. Since the volume of the radiationaperture body has been significantly reduced, significantly less brassmay be needed resulting in an even greater cost savings.

The radiation source may include a radiation output having a firstdiameter, and the opening in the cover may have a second diameter lessthan the first diameter. This results in the radiation aperture bodybeing fully exposed to the radiation.

To prevent unwanted radiation from passing through an interface betweenthe radiation aperture body and the aperture holder and cover, theradiation aperture body may comprise a frusto-conical first portion, andthe aperture receiving passageway may have a corresponding shape to thefrusto-conical first portion. Similarly, the radiation aperture body maycomprise a frusto-conical second portion, and the opening of the covermay have a corresponding shape to the frusto-conical second portion. Therecessed end of the aperture holder and the cover may also define athreaded joint therebetween.

The radiation aperture body may comprise at least one alignment edgeextending outwards therefrom, and the aperture-receiving passageway mayfurther include at least one recess receiving the at least one alignmentedge.

Another aspect of the present invention is directed to an apertureassembly for radiation therapy, as described above.

Yet another aspect of the present invention is directed to a method formaking an aperture assembly for radiation therapy. The method maycomprise forming a radiation aperture body having a shaped openingtherein to control a radiation dosing profile. An aperture holder havinga disk shape, an aperture-receiving passageway therein to receive theradiation aperture body, and a recessed end is formed. The method mayfurther comprise forming a cover received within the recessed end of theaperture holder, with the cover to retain the radiation aperture bodywithin the aperture holder, and with the cover having an opening alignedwith the shaped opening in the radiation aperture body.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a radiation therapy apparatus in accordancewith the present invention.

FIG. 2 is an exploded perspective view of the aperture assemblyillustrated in FIG. 1.

FIG. 3 is a cross-sectional side view of the aperture assemblyillustrated in FIG. 1.

FIG. 4 is a top view of the aperture holder illustrated in FIG. 2without the radiation aperture body within the aperture-receivingpassageway.

FIG. 5 is a flowchart illustrating a method for making the apertureassembly for radiation therapy illustrated in FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will now be described more fully hereinafter withreference to the accompanying drawings, in which preferred embodimentsof the invention are shown. This invention may, however, be embodied inmany different forms and should not be construed as limited to theembodiments set forth herein. Rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of the invention to those skilled in the art. Likenumbers refer to like elements throughout.

Referring initially to FIG. 1, a radiation therapy apparatus 10 includesa housing 12, a radiation source 14 carried by the housing, at least oneaperture assembly 20 carried by the housing, and a radiation filter 18carried by the housing. In the illustrated embodiment, three apertureassemblies 20 are stacked on top of one another. If the penetrationenergy of the radiation is low, then only one aperture assembly 20 maybe sufficient to block radiation from healthy tissue within the patient.However, if the penetration energy of the radiation is high, thenmultiple aperture assemblies 20 may be combined to provide a totalthickness necessary to block radiation from healthy tissue within thepatient. Even though a single aperture assembly 20 having the samecombined thickness could be used, the weight would make it difficult tohandle.

The radiation filter 18 is also known as a range compensator and filtersthe radiation. Filter is broadly used to include controlling theintensity or range of the radiation depending on modality, as readilyunderstood by those skilled in the art. The radiation filter 18 isspecifically designed for the patient. The radiation filter 18 may bemachined from a solid piece of material, and is mounted directly in thepath of the radiation beam, as disclosed in U.S. Pat. No. 6,980,871.This patent is assigned to the current assignee of the presentinvention, and is incorporated herein by reference in its entirety. Theunique three-dimensional geometry of each radiation filter 18 providesthe conformal radiation dose distributions required by the patient.

The illustrated radiation source 14 is configured to generate protons.The radiation source 14 includes a particle accelerator, either asynchrotron or a cyclotron, to accelerate the protons to variableenergies into a beam transport line. A synchrotron contains a ring ofmagnets that constrains the protons so that they travel in a set pathinside a high vacuum chamber. During each revolution of travel throughthe chamber, the protons gain an increment of energy from the radiofrequency power. After many cycles, the protons reach the energyrequired by the specific treatment planning system and are extractedfrom the ring of magnets into the beam transport line, which directs theprotons to the aperture assemblies 20. Even though the illustratedradiation source 14 is a proton radiation source, the aperture assembly20 is readily applicable to other types of radiation sources, such aselectrons or photons, as readily appreciated by those skilled in theart.

The aperture assembly 20 will now be discussed in greater detail. Eachaperture assembly 20 includes a radiation aperture body 30, an apertureholder 40 and a cover 50, as illustrated by the exploded view in FIG. 2and the cross-sectional view in FIG. 3. The radiation aperture body 30may also be referred to as an aperture. The radiation aperture body 30has a shaped opening 32 therein specific to the patient to control aradiation dosing profile of the protons. The radiation aperture body 30is typically made out of brass, for example. As an alternative to brass,other high density materials capable of blocking protons may be used.

The aperture holder 40 has an aperture-receiving passageway 42 thereinreceiving the radiation aperture body 30, and has a recessed end 44. Thecover 50 is received within the recessed end 44 of the aperture holder40 and retains the radiation aperture body 30 within the apertureholder. The illustrated aperture holder 40 has a disk shape. The shapeof the aperture holder 40 is not limited to a disk shape. Instead, theshape is based upon the profile of the radiation output or snout of theradiation source 14. In other embodiments, the aperture holder 40 mayhave a rectangular shape, for example.

The cover 50 has an opening 52 aligned with the shaped opening 32 in theradiation aperture body 30. Aligned in this instance means that theopening 52 is not overlapping or blocking the shaped opening 32 in theradiation aperture body 30. The aperture holder 40 and cover 50 aretypically made out of a non-brass material, such as stainless steel, forexample. As an alternative to stainless steel, other high densitymaterials capable of blocking protons may be used.

As a result of the aperture holder 40 and the cover 50, the volume ofthe radiation aperture body 30 has been significantly reduced. Since theaperture holder 40 and the cover 50 are reusable, significantly lessbrass is needed, a greater cost savings may be achieved. As discussed inthe background section, prior art radiation aperture bodies were notfully exposed to the protons. In other words, the outside diameter ofthe radiation aperture body exceeded the diameter of the radiationoutput. This ensured that there were no interfaces being exposed to theprotons that would allow the protons to penetrate through and onto thepatient receiving treatment.

In sharp contrast, the radiation aperture body 30 is fully exposed tothe protons. In other words, the radiation source 14 includes aradiation output having a first diameter d₁, and the opening 52 in thecover 50 has a second diameter d₂ less than the first diameter, asillustrated in FIG. 3. This notably causes the interface 57 between theradiation aperture body 30 and cover 50, as well as the interface 55between the radiation aperture body 30 and the aperture holder 40, to befully exposed.

To prevent unwanted radiation from passing through the interfaces 57, 55between the radiation aperture body 30 and the aperture holder 40 andcover 50, the radiation aperture body has a frusto-conical first portion36, and the aperture receiving passageway 42 has a corresponding shapeto the frusto-conical first portion. Similarly, the radiation aperturebody 30 has a frusto-conical second portion 38, and the opening 52 ofthe cover 50 may have a corresponding shape to the frusto-conical secondportion.

As a result of the frusto-conical portions 36, 38 of the radiationaperture body 30, the interfaces 57, 55 are angled. This advantageouslyreduces any chance of unwanted protons making their way to the patient,as compared to vertical interfaces, by increasing the relative anglebetween the radiation particles and the interfaces 57, 55. Thefrusto-conical portion 36 also allows the radiation aperture body 30 tobe press fit into the aperture holder 40, ensuring unwanted radiationdoes not pass through the interface 55. Similarly, the frusto-conicalportion 38 also allows the cover 50 to be press fit onto the radiationaperture body 30, ensuring unwanted radiation does not pass through theinterface 57.

In other embodiments, the radiation aperture body 30 may include onlyone frusto-conical portion 36 or 38. The other non-frusto-conicalportion may be configured so that one of the interfaces 57 or 55 is at avertical angle with respect to an upper surface of the aperture holder40.

Another area of concern for radiation leakage is at the interface 45between the aperture holder 40 and the cover 50. To address thisconcern, the recessed end 44 of the aperture holder 40 and the cover 50define a threaded joint therebetween. In other words, the recessed end44 and the cover 50 are threaded for engaging one another to define thethreaded joint. The interface 45 may also be angled.

To place the radiation aperture body 30 in a desired orientation, theradiation aperture body includes at least one alignment edge 37extending outwards therefrom, as illustrated in FIG. 2. Theaperture-receiving passageway 42 include at least one recess 41receiving the at least one alignment edge, as illustrated in FIG. 4. Inthe illustrated embodiment, there are three alignment edges 37 and threecorresponding recesses 41. The alignment edges 37 and recesses 41prevent spinning of the radiation aperture body 30 once placed in theaperture-receiving passageway 42.

Referring now to the flowchart 100 in FIG. 5, another aspect is directedto a method for making an aperture assembly 20 for radiation therapy.The method comprises, from the start (Block 102), forming a radiationaperture body 30 at Block 104 having a shaped opening 32 therein tocontrol a radiation dosing profile. An aperture holder 40 is formed atBlock 106 having a disk shape, an aperture-receiving passageway 42therein to receive the radiation aperture body 30, and having a recessedend 44. The method further comprises forming a cover 50 at Block 108that is received within the recessed end 44 of the aperture holder 40.The cover 50 retains the radiation aperture body 30 within the apertureholder 40. The cover 50 has an opening 52 aligned with the shapedopening 32 in the radiation aperture body 30. The method ends at Block110.

Many modifications and other embodiments of the invention will come tothe mind of one skilled in the art having the benefit of the teachingspresented in the foregoing descriptions and the associated drawings.Therefore, it is understood that the invention is not to be limited tothe specific embodiments disclosed, and that modifications andembodiments are intended to be included within the scope of the appendedclaims.

That which is claimed is:
 1. A radiation therapy apparatus comprising: ahousing; a radiation source carried by said housing; at least oneaperture assembly carried by said housing and comprising a radiationaperture body having a shaped opening therein to control a radiationdosing profile, an aperture holder, an aperture-receiving passagewaytherein receiving said radiation aperture body, and having a recessedend, and a cover received within the recessed end of said apertureholder and retaining said radiation aperture body within said apertureholder, said cover having an opening aligned with the shaped opening insaid radiation aperture body, and said radiation aperture body, theaperture receiving passageway of said aperture holder and the opening ofsaid cover having angled interfaces therebetween; a radiation filtercarried by said housing.
 2. The radiation therapy apparatus according toclaim 1 wherein said at least one aperture assembly comprises aplurality of stacked aperture assemblies.
 3. The radiation therapyapparatus according to claim 1 wherein said radiation aperture bodycomprises a frusto-conical first portion; and wherein the aperturereceiving passageway has a corresponding shape to the frusto-conicalfirst portion.
 4. The radiation therapy apparatus according to claim 1wherein said radiation aperture body comprises a frusto-conical secondportion; and wherein the opening of said cover has a corresponding shapeto the frusto-conical second portion.
 5. The radiation therapy apparatusaccording to claim 1 wherein the recessed end of said aperture holderand said cover define a threaded joint therebetween.
 6. The radiationtherapy apparatus according to claim 1 wherein said radiation aperturebody comprises at least one alignment edge extending outwards therefrom;and wherein the aperture-receiving passageway further includes at leastone recess receiving the at least one alignment edge.
 7. The radiationtherapy apparatus according to claim 1 wherein said radiation aperturebody comprises brass.
 8. The radiation therapy apparatus according toclaim 1 wherein said aperture holder and said cover each comprisesstainless steel.
 9. The radiation therapy apparatus according to claim 1wherein said radiation source generates protons.
 10. An apertureassembly for radiation therapy comprising: a radiation aperture bodyhaving a shaped opening therein to control a radiation dosing profile,said radiation aperture body comprising a frusto-conical first portion;an aperture holder, an aperture-receiving passageway therein receivingsaid radiation aperture body, and having a recessed end; and a coverreceived within the recessed end of said aperture holder and retainingsaid radiation aperture body within said aperture holder, said coverhaving an opening aligned with the shaped opening in said radiationaperture body and having a shape corresponding to the frusto-conicalfirst portion; said radiation aperture body, the aperture receivingpassageway of said aperture holder and the opening of said cover havingangled interfaces therebetween.
 11. The aperture assembly according toclaim 10 wherein said aperture holder has a disk shape.
 12. The apertureassembly according to claim 10 wherein said aperture holder has arectangular shape.
 13. The aperture assembly according to claim 10wherein said radiation aperture body comprises a frusto-conical secondportion; and wherein the aperture receiving passageway has acorresponding shape to the frusto-conical second portion.
 14. Theaperture assembly according to claim 10 wherein the recessed end of saidaperture holder and said cover define a threaded joint therebetween. 15.The aperture assembly according to claim 10 wherein said radiationaperture body comprises at least one alignment edge extending outwardstherefrom; and wherein the aperture-receiving passageway furtherincludes at least one recess receiving the at least one alignment edge.16. The aperture assembly according to claim 10 wherein said radiationaperture body comprises brass.
 17. The aperture assembly according toclaim 10 wherein said aperture holder and said cover each comprisesstainless steel.
 18. A method for operating a radiation therapyapparatus comprising: providing a radiation source to generate aradiation output having a first diameter; positioning at least oneaperture assembly within the radiation output of the radiation source,the at least one aperture assembly comprising a radiation aperture bodyhaving an outside diameter less than the first diameter and an exposedupper surface with a shaped opening therein to control a radiationdosing profile, an aperture holder, an aperture-receiving passagewaytherein receiving the radiation aperture body, and having a recessedend, and a cover received within the recessed end of the aperture holderand retaining the radiation aperture body within the aperture holder,the cover having an opening aligned with the exposed upper surface ofthe radiation aperture body so as to define an interface therebetweenthat is exposed to the radiation output, the radiation aperture body,the aperture receiving passageway of the aperture holder and the openingof the cover having angled interfaces therebetween; and positioning aradiation filter adjacent the at least one aperture assembly.
 19. Themethod according to claim 18 wherein the radiation aperture bodycomprises a frusto-conical first portion; and wherein the aperturereceiving passageway has a corresponding shape to the frusto-conicalfirst portion.
 20. The method according to claim 18 wherein theradiation aperture body comprises a frusto-conical second portion; andwherein the opening of the cover has a corresponding shape to thefrusto-conical second portion.
 21. The method according to claim 18wherein the recessed end of the aperture holder and the cover define athreaded joint therebetween.
 22. The method according to claim 18wherein the radiation aperture body comprises at least one alignmentedge extending outwards therefrom; and wherein the aperture-receivingpassageway further includes at least one recess receiving the at leastone alignment edge.
 23. The method according to claim 18 wherein theradiation aperture body comprises brass.
 24. The method according toclaim 18 wherein the aperture holder and the cover each comprisesstainless steel.